Bluetooth BLE spec Tutorial: http://www.wowotech.net/sort/bluetooth
Online pdf turn Word: http://www.pdfdo.com/pdf-to-word.aspx
python resources: https://www.cnblogs.com/BlameKidd/p/9911907.html
esp32 private blog: https://blog.csdn.net/qq_27114397/article/details/81147547
c ++ official website: http://www.cplusplus.com/info/
Online tools --- home owners: http://tool.chinaz.com/